I’m not sure what publishing platform you are using for the Mattermost blog, but I suggest you review your work-flow involving draft posts. Somehow your as-yet unpublished posts are ending up in the RSS feed—or at least their titles are. On multiple occasions I have been notified of posts that don’t exist yet. Most recently I see that “Mattermost 1.0” has been “released with personalization, rich formatting and data center readiness”. That seems like its jumping the gun just a little bit.
I assume these are drafts being started ahead of time, but somehow they need to be marked as being unpublished before they are saved the first time rather than after or whatever bug in the feed algorithm allows this needs to be fixed.